1. Field
This invention relates generally to a tool for handling high torque, more specifically, a locking nut for a handling pole in a nuclear reactor pressure vessel.
2. Description of Related Art
Repairs and inspections performed within a reactor pressure vessel (RPV) such as a boiling water reactor (BWR) are generally performed with ropes and poles for manual manipulation of tools and/or delivery of dedicated automated tools. The RPV is generally a cylindrical shaped vessel and is closed at both ends (e.g., a bottom head and a removable top head). During a reactor shut down, the top head of the RPV is removed so as to inspect or repair a selected component within. Other components in the RPV located between a top guide and a core plate or below the core plate may also be removed. To perform the inspections and/or repairs, an operator stands on a bridge positioned over the RPV and lowers the tool using ropes and poles, which may extend about eighty (80) feet below. The ability to perform such inspections and/or repairs depends on the dexterity of the operator.
Due to the difficulty in accessing certain locations within the RPV, performing the repairs and/or inspections at such locations can be time consuming and burdensome. It is desirable to limit the time required to perform the repairs and/or inspections in a RPV due to the enormous daily cost of the reactor being shut down (up to almost a million dollars a day in lost revenue). Reducing the amount of time required to perform such inspections and/or repairs also would facilitate reducing radiation exposure to operators, technicians and maintenance personnel, for example.
An approach to repairing and/or inspecting equipments in the RPV has been to use handling poles to attach tools for repairing and servicing. The handling poles are light-weight and thus easy to maneuver within the RPV. Further, handling poles may be designed specifically to handle high-torque. The handling poles may be generally constructed in 10-foot sections and assembled to work in depths of over 80 feet.
However, conventional handling poles typically employ a single nut to connect and lock the adjoining poles together. The single nut is typically hand tightened by an operator to lock the two poles together, and then an adhesive tape (i.e., duct tape) is attached around the nut to prevent it from inadvertently unlocking during operation. However, use of adhesive tape is not an effective manner to retain the nut on two adjoining metal poles, because the adhesive tape maybe exposed to hot water which degrades the adhesive on the tape and cause separation of the adjoining poles. Even further, during pole disconnection, it maybe necessary to first unwrap the tape. This action causes droplets of contaminated water to occasionally be expelled from the tape and may contact workers causing skin contamination. The degraded tape also leaves the glue behind on the pole sections in which radiological contaminations may stick to the adhesive tape residue and cause radiological exposure to operators and radioactive contamination issues.